Prime Minister Shinzo Abe paid his respects at a shrine honouring Japan's war dead in an unexpected visit today that drew sharp rebukes from China and South Korea, who warned that the move celebrates his country's militaristic past and could further sour relations.

On his first anniversary of taking office, Abe spent about 15 minutes at the Yasukuni shrine in central Tokyo. "I prayed to pay respect for the war dead who sacrificed their precious lives and hoped that they rest in peace," he told waiting reporters afterward.

Japanese politicians' visits to Yasukuni have long caused friction with China and both Koreas, because the 2.5 million war dead enshrined there include 14 class A war criminals from World War II - national leaders who were either executed or died in prison or during their trials. Japan colonized Korea and occupied parts of China, often brutally, before and during World War II.

It was the first visit to the Shinto-style war shrine by a sitting Japanese prime minister since Junichiro Koizumi went in 2006 to mark the end of World War II. Abe previously visited Yasukuni while out of office.

Abe, a nationalist who advocates revising Japan's pacifist constitution, has always wanted to visit Yasukuni as prime minister, but he still surprised some analysts, who thought he might take a pragmatic approach to leadership that focused on reviving the economy and trying to avoid alienating neighbours.

The United States expressed disappointment "that Japan's leadership has taken an action that will exacerbate tensions with Japan's neighbours."

TV cameras followed Abe inside the shrine property, but were not allowed in the inner shrine. The prime minister was dressed formally in black jacket with tails and striped, grey pants. There is no fixed dress code for shrine visits, but conservative lawmakers usually dress formally to be polite and dignified.

Abe said criticism that visits to Yasukuni are an act of worshipping war criminals is based on a misunderstanding.

"Unfortunately, a Yasukuni visit has largely turned into a political and diplomatic issue," he said. "It is not my intention to hurt the feelings of the Chinese and Korean people."

He said he believes Japan must never wage war again: "This is my conviction, based on the severe remorse for the past."

The visit "has created major new political obstacles for already strained Sino-Japanese relations, and China won't ever tolerate it. Japan must bear all the responsibilities caused by Abe's move," Wang said, adding that if Japan intentionally continues to exacerbate tensions and antagonism, "China will surely keep it company to the end."

"What Abe has done is leading Japan in a very dangerous direction. Lessons from history must be learned. The international community including China must heighten its vigilance and never allow the wheel of history to be turned back," Wang said.

China's state broadcaster CCTV closely covered news of the shrine visit, wrapping it into an already critical feature of Abe's past year in office. The foreign ministry's condemnation of the visit was the network's top news item on its noon nationwide bulletin.

South Korea's minister of Culture, Sports and Tourism, Yoo Jinryong, labeled the visit "an anachronistic act" that "hurts not only the ties between South Korea and Japan but also fundamentally damages the stability and cooperation in Northeast Asia." His briefing was broadcast live on TV.

A statement released by the US Embassy in Tokyo took note of Abe's expression of remorse, but said "the United States hopes that both Japan and its neighbors will find constructive ways to deal with sensitive issues from the past."

Adding to the unease of Japan's neighbors is Abe's push to expand the military at a time of rising tensions over a cluster of uninhabited islands in the East China Sea claimed by both Japan and China.

Japanese political scientist Koichi Nakano said the visit answered questions on whether Abe is a pragmatist or a rabid nationalist.

"I think we know where his beliefs lie," said Nakano, a professor at Sophia University in Tokyo. "He's not in politics because of economics. He's a conviction politician just like Margaret Thatcher was. Pragmatism and conviction don't go very well together."